ZTE claims VDSL2 vectoring breakthrough

Stuart Corner
Sunday, 24 October 2010 16:28

Business IT - Technology

ZTE has announced what it claims is the world's first system-level VDSL2 vectoring prototype - technology that increases the carrying capacity of copper pairs in the telephone network by managing all the pairs in a multi-pair cable so as to minimise crosstalk between discrete pairs.

According to ZTE, its prototype device, dubbed the ZXDSL 9836, "automatically analyses interference between line pairs and eliminates the major interference, achieving 100Mbps data downstream speeds through copper lines [and] is a significant breakthrough that paves the way for the commercial use of copper lines in large-scale network deployments."

ZTE says that its ZXDSL 9836 compact DSLAM can support up to 192 VDSL2 lines and "provides vectoring for all access lines from the same remote access node in a number of application modes from small-capacity FTTB (fibre-to-the-building) projects to large-capacity FTTC (fibre-to-the-cabinet) deployments, which cannot be achieved by current card-level vectoring solutions."

ZTE's announcement, however omitted a key piece of information: it gave no indication of how the throughput of copper pairs managed by its vectoring technology degrades with distance, as compared to standard VDSL2.

According to Wikipedia: "VDSL2 deteriorates quickly from a theoretical maximum of 250Mbps at source to 100Mbps at 0.5 km and 50Mbps at 1km, but degrades at a much slower rate from there, and still outperforms VDSL. [Beyond] 1.6 km its performance is equal to ADSL2+."

Techniques for increasing the capacity of copper by managing multiple pairs have been known for years, but in the past the massive amounts of processing technology needed to do this over close to 200 pairs, as ZTE claims to have done, has not been available.

Back in 2007 Telstra CTO, Hugh Bradlow, told analysts and the company's annual investor day "We're already working on the next two generations of copper-based technology, VDSL2 and dynamic spectrum management, both of which will increase the speeds so that the copper technology has the potential to get up to 100Mbps."

In April 2008, Huawei announced its Xpert LAS,  billed as "the industry's first hybrid access line assurance solution." Huawei claimed that Xpert LAS "implements the leading DSM (Dynamic Spectra Management) technology'¦to solve the DSL crosstalk & interference bottleneck in an efficient and practical way." Huawei claimed that Xpert LAS "improves ADSL2+/ VDSL2 performance by over 30 percent...[and] helps operators to expand their IPTV offerings or other bandwidth-consuming services in the copper bundle."

In April this year, Alcatel-Lucent claimed to have as achieved a DSL downstream bandwidth of 300Mbps over 400metres and 100Mbps at 1km using two copper pairs and a technology known as 'DSL Phantom Mode'. This was followed in September by a claim from Huawei that its 'SuperMIMO' technology could achieve a downstream rate of 700Mbps at a distance of 400 metres using four copper pairs.